A method for controlling sound in a space includes an sound field reproducing method of reproducing a specific sound field, an active noise control method of reducing a magnitude of sound of a space using a plurality of active sound sources, a method of changing an interval between sound sources arranged in a specific form, a method of increasing acoustic power radiated at a specific angle by changing time delay between sound sources and a magnitude of each sound source, and the like. Recently, research on personalized sound zone control has actively been conducted to deliver only a specific sound source according to positions of a listener in a closed space such as the inside of a vehicle compartment or a living room.
For example, Korean Patent Laid-Open Publication No. 10-2010-0066826 (Directional Sound Generating Apparatus and Method) proposes a method of radiating sound to a specific region but discloses only a technique of concentrating sound to a specific region by disposing a high-directive speaker and the like. In this manner, the related art method of controlling sound of a space using a plurality of sound sources merely changes time delay between sound sources and an input magnitude thereof and merely changes only a direction of sound sources using a sound source arrangement in a limited form, without considering a position of a listener in a predetermined space.
Meanwhile, Korean Patent Laid-Open Publication No. 10-2014-0138907 (Method of Applying Integrated or Hybrid Sound-Field Control Strategy) discloses a method of applying an integrated control strategy for regeneration of multi-channel audio signals in two or more sound zones but all the speakers in use are limited to have the same acoustic characteristics. However, in the case of calculating an acoustic transfer function on the assumption that all the speakers in use have the same acoustic characteristics, even a speaker which contributes less to form an actual personalized sound zone is forcibly excited or a speaker is forcibly excited even at a frequency band having a low contribution to form a personalized sound zone, and thus, there is a high possibility of including a numerical error and it is not desirable in terms of efficiency such as the amount of calculation for calculating a control filter, and the like.
In particular, inside a vehicle compartment in which speakers having a variety of acoustic characteristics to form an optimal acoustic environment such as a tweeter for a high range, a mid-woofer or a full-range for a mid-part, a sub-woofer for a low range, and the like, are combined to be used, a contribution of each speaker appears to be different in forming a personalized sound zone in a specific zone, and thus it is more important to consider acoustic characteristics of the individual speakers. Further, in the case of the related art personalized sound zone control, a control filter is calculated on the assumption that such a contribution is regarded to be included in a acoustic transfer function between a speaker and a microphone positioned in a set zone or all the speakers have the same characteristics, and in this control method, a speaker with little contribution may be utilized in calculating the control filter in a frequency region with a low contribution to act as a sort of numerical error and an acoustic signal, although weak, is discharged when actually forming an sound field and heard as noise.